This invention relates to apparatus for positioning the spreader for grasping, loading and unloading of containers or other handling articles of a rectangular parallelepiped shape. More particularly, the invention is concerned with a novel apparatus for positioning such spreader relative to the handling article loading and unloading bed of a freight car, the handling article loading and unloading bed of a truck or a handling article of the type described, which apparatus has particular utility in article handling apparatus for carrying out unloading of desired articles from a train of freight cars and transfer of such handling articles to a predetermined zone or trucks and vice versa.
Although the articles handled by the apparatus according to the invention are not limited to containers, the invention will be described hereinafter by way of example with reference to a container loading and unloading crane mounting such a spreader for better understanding of the invention.
At a terminal or yard, when loading and unloading containers between freight cars and trucks, in order to load and unload containers accurately, quickly and efficiently of the gantry type crane is usually equipped there. Such a container loading and unloading crane has been proposed by our company in Japanese Patent Application No. 31653/72 (Laid-Open Patent Application No. 99832/73 and Patent Publication No. 35298/76) and Japanese Patent Application No. 31654/72 (Laid-Open Patent Application No. 99833/73). Also, an invention has been developed by us in connection with full automation of container loading and unloading operation at a container terminal or yard so as to effect full automation of a container yard. Such a invention has been issued as U.S. Pat. No. 3,861,100.
When using a container loading and unloading crane automatically, it is necessary to perform the following operations:
1. Providing an address to each of freight cars with respect to a position on the ground in order to indicate to the crane the container to be handled; PA1 2. Positioning the crane to an instructed location. This involves moving the crane to the predetermined instructed position by judging the travelling direction of the crane, the traversing direction of a trolley disposed on the crane for supporting the spreader for grasping articles, and the direction of lifting movement of the spreader after comparing the present position of the crane with the instructed position; and PA1 3. Positioning the spreader for grasping the container supported by the trolley on the crane with respect to a container, the bed of a freight car or the bed of a truck. That is, a container grasping operation is performed by registering twist lock pins of the container grasping spreader with respective openings formed at four corners of the upper edge of the container. But, it is very difficult to stop the crane precisely at the instructed position within about .+-.10 mm. Thus it is necessary to detect deflection in the relative positions of the container grasping spreader and the container, the bed of the freight car or the bed of the truck, and then to adjust finely the position of the spreader by slightly moving the latter so as to position the spreader accurately with respect to the container.
Of the three operations described above, the operation set forth in paragraph (3) must be performed with a high degree of precision because it is an important operation in grasping, loading and unloading containers safely and positively. In positioning a spreader with respect to a container, the bed of a freight car or a truck, it has hitherto been usual practice to use a container itself as a target for detection when the container is to be grasped and to use container clamping fixtures attached to freight cars or the like as targets for detection when the container is to be unloaded. Containers, the bed of a freight car and a truck have no member mounted thereon which would serve as a target for detection. Thus a large number of contact-type sensor and non-contact-type sensor must be used as a sensor, and this is a disadvantage for the sensors and their logical circuit to be complex in construction. Also, spreader positioning apparatus of the prior art use basically mechanical sensor of the contact type in many cases. There is a defect when using such sensors, damaged by the container or the container clamping fixtures mounted on freight cars.
In order to solve these problems arising with regard to the prior art and to obviate the disadvantages thereof, an invention has been developed in connection with positioning of a spreader and disclosed in Japanese Patent Application No. 145570/74 (Laid-Open Patent Application No. 72045/76). According to this invention, detecting plate serving as targets for detection are attached only to the bed of a freight car and a truck, and the sensor is changed to the non-contact type so as to simplify the control system for positioning a spreader with respect to the bed of a freight car or a truck.
It should be noticed that the aforesaid apparatus for positioning a spreader used no detected elements attached to containers themselves and serving as targets for detection. Therefore, according to the invention, the spreader is provided as means for positioning the spreader with respect to a container or particularly for positioning the spreader with respect to the container carrying freight car travelling direction, with a plurality of detectors of the non-contact type connected to a circuit capable of making a logical decision and effecting control accordingly. It is true that this apparatus for positioning a spreader has a more simplified detecting mechanism than similar apparatus of the prior art. However, this apparatus has a disadvantage in simple system of the spreader because it is not easy to carry out its maintenance and inspection.